Field of the Invention
The present invention relates to an image pickup apparatus, an image pickup device, a control method for the image pickup apparatus, and a control method for the image pickup device, and in particular, relates to technique performing photometry using an image pickup device.
Description of the Related Art
When obtaining one frame that constitutes a still image or a video image, an image pickup apparatus equipped with a CMOS sensor achieves a global electronic shutter by accumulating electric charges occurred by photoelectric conversion to photoelectric conversion parts and transferring the electric charges from the photoelectric conversion parts to accumulation parts simultaneously for all pixels. For example, United States Patent Application 20150264244A1 proposes a technique that optimizes a ratio of a saturation charge amount of a photoelectric conversion part to a saturation charge amount of a charge accumulation part according to timing of transferring an electric charge to the charge accumulation part in a charge accumulation period and that reduces pixel size while increasing the saturation charge amount.
However, the technique disclosed in the above-mentioned application may cause saturation of the photoelectric conversion part because of delay of charge transfer from the photoelectric conversion part to a charge accumulation part when sudden bright light like reflected flash light (reflected light from an object at a time of electronic flash emission) is received. Moreover, since controllable unit time is restricted in a case of performing charge transfer multiple times during photoelectric conversion, a desired high-luminance limit of photometry may not be attained. Photometry of object luminance using such a CMOS sensor as a photometry sensor lowers accuracy of a photometry value calculated. For example, an object distance (distance from an image pickup device to an object) is unknown at a time of photometry of the reflected flash light. Accordingly, when an electronic flash device emits light of a predetermined emission amount, the photoelectric conversion part may be saturated by the reflected flash light because of a short object distance. Thus, the lowered photometry accuracy may disable appropriate calculation of a flash emission amount for main photographing, which disables flash photographing in correct exposure.